Platforming process



TEMPERATURE REQUIRED TO Dec. 4, 1962 PRODUCE DEBUTANIZED REFORMATEYIELD, %V

I00 F IO OCTANE NUMBER REFORMATE, F

SULFUR ON CATALYST, %W

D. BALDWIN, JR, ETAL 3,067,130

PLATFORMING PROCESS Filed May 9, 1960 1 l l l l 2 3 4 5 6 7 8 9 -IOCATALYST AGE, BBL/LB CATALYST AGE, B BL/LB FIG. 3

| l l 2 3 4 5 6 708 9 IO DESULFURIZED NAPHTHA, BBL/LB THEIR ATTORNEY3,067,130 PLATFQRMING PRUCESS Douglas Baldwin, Jan, Genoa, and MaxwellNager, Pasadena, Tex., assignors to Shell Gil Company, New York, N.Y., acorporation of Delaware Filed May 9, 1966, Ser. No. 27,639 1 Claim. (Cl.2tl$-140) This invention relates to the upgrading of naphthas byPlatforming.

Platforming is herein defined as a catalytic reforming process in whicha hydrocarbon fraction containing naphthenes and paraffins and boilingin the gasoline boiling range is contacted in the vapor phase and in thepresence of a substantial pressure of hydrogen with a catalystcontaining platinum on a suitable support such as alumina underdehydrogenating conditions of temperature e.g., 800l000 F., whereby aproduct of improved octane number is obtained.

In Platforming the main reactions leading to improvement of the octanenumber are the dehydrogenation and dehydroisomerization of naphthenesand dehydrocyclization of paraflins to aromatic hydrocarbons and thehydrocracking of low octane normal parafiins. Minor reactions which alsooccur are the isomerization of normal paraflins, and some condensations.During the operation the catalyst gradually loses activity due, at leastin part, to the accumulation of tarry carbonaceous deposits.

In the usual practice the conditions of Platforming severity areinitially adjusted to give a product having the desired octane numberand then the temperature is gradually raised to counteract the declinein the activity of the catalyst until a point is reached where furthertemperature increase is impractical because of temperature limitationsof the equipment or other reasons. At this point the run is stopped.

The severity of the Platforming operation is primarily a function of thetemperature, pressure, and space velocity. Generally in commercialpractice the severity is controlled by the temperature as explainedabove. The pressure and space velocity normally are not altered over anyappreciable range in a given Platforming plant.

If runs are made with a given feed stock over a range of severities twothings are observed. First, as the severity is increased the octanenumber of the product increases but the yield of product decreases. Thisthen gives a yield vs. octane number curve and it will be apparent thatit is desirable to operate at the minimum severity affording thenecessary octane number in order to maximize the yield. Secondly, as theseverity is increased the rate at which the catalyst loses activityincreases. It is customary to express this rate of loss of activity ofthe catalyst in term of degrees of temperature increase required tomaintain the octane number per barrel of feed per pound of catalyst.Thus, for example, a decline rate of F. means that for each barrel offeed passed per pound of catalyst the reaction temperature must beincreased 10 F. in order to maintain a constant quality of the product.If the maximum temperature increase in such a case is 100 F. (e.g., 850to 950 F.) it is seen that the maximum catalyst life under theseconditions is 10 barrels per pound of catalyst. The decline rate is notnecessarily constant throughout a run but is generally approximately Incommercial practice there are three types of Platforming operationsherein designated as continuous, semiregenerative and regenerative. AsWill be evident from the above, when mild conditions (i.e., lowseverity) are sufficient to obtain a product of satisfactory octanenumber the catalyst decline rate is very low and the process may beoperated continuously for many months producing dfiblfid Patented Dec.4, 1962 the maximum quantity of product. In this case when the catalystis spent it is replaced by a charge of fresh catalyst or catalyst thathas been reworked in a separate plant. The cost of the catalyst is ofthe order of $5.00 per pound.

Under conditions of somewhat greater severity the rate of catalystdecline is such that less than about 20 barrels of feed may be processedper pound of catalyst. To replace a catalyst under these conditionswould result in a cost for catalyst alone of at least around 25 centsper barrel. This would be prohibitive. In this case it is the custom toregenerate the catalyst in situ. However, since regenerations are fewand infrequent the provision of regular regeneration facilities is notjustified. The whole plant is shut down during the regeneration. Thistype of operation with infrequent regeneration is calledsemi-regenerative Platforming.

Under still more severe conditions the decline rate becomes so rapidthat very frequent regeneration is required. In this case it would beuneconomical to shut down the whole plant at short intervals and toavoid this it is the practice to arrange the reactors with suitableplumbing so that each may be taken separately off stream and regeneratedwhile the process is continued in the other reactors. This last methodof operation is designated regenerative Platforming.

The process of the present invention relates to semiregenerativePlatforming. It has no application in continuous or regenerativePlatforming.

When starting up a non-regenerative Platforming run with a fresh batchof catalyst it has been found desirable in some cases to curtail thehigh initial activity of the catalyst by including some sulfur in thefeed during the first few hours of processing. This prevents so calledrunaway hydrocracking which is highly exothermic and which is sometimesencountered at the start up. It is well known, however, that innon-regenerative Platforming sulfur in the feed is a poison to thecatalyst and consequently it is the practice to pretreat the Platformingfeed to desulfurize it. This is normally done by hydrodesulfurizing thefeed with a supported cobalt molybdenum catalyst using off-gas from thePlatforming operation. Also in regenerative Platforming sulfur in thefeed is most undesirable and in fact cannot be tolerated because thecatalyst reactor walls, piping, etc. become somewhat sulfurized and uponregeneration oxides of sulfur are formed which ruin the catalyst.Moreover, scale which is formed in the heater, piping, etc. tends todeposit in the catalyst bed and thereby causes plugging which results inexcessive pressure drop.

It has now been found, however, that in semi-regenerative Platformingthe inclusion of sizeable amounts of sulfur in the feed is desirable andshould be used throughout the run provided that a desulfurized feed isused during the last approximately 2 barrels per pound of the run. Thus,it has been discovered that in semi-regenerative Platforming,particularly to an F10 octane level of around or higher, the yield andcatalyst stability are both considerably improved by incorporatingsulfur in a concentration of around 300 ppm. in the feed and that suchoperation is possible provided that a sulfur-free feed is used duringthe last approximately 2 barrels per pound. It has been found that afterusing a feed containing sulfur it requires about 2 barrels per pound ofsulfur-free feed to desulfurize the catalyst to a point where it can beregenerated. The magnitude of the effects Will be shown by the followingexamples in which reference will be made to the accompanying drawing.

FIGURE 1 of the drawing is a graph showing the temperature required toprovide 100 Fl0 Platformate vs. the catalyst age under semi-regenerativeconditions.

FIGURE 2 is a graph showing the debutanized Platformate yield vs.catalyst age in the same semi-regenerative runs. FIGURE 3 is a graphshowing the sulfur content of the catalyst after use with asulfur-containing feed and during subsequent treatment of a desulfurizedfeed.

In these examples the feeds were heavy naphthas having the propertiesshown in table 1.

These feeds were Platformed with Universal Oil Products Co. commercialR-8 Platforming catalyst under the conditions shown in Table 2.

TABLE 2 Example 1 2 3 Catalyst UOP, R-8 UOP, R-S UOP, R-B OutletPressurc,p.s.i.g 350 350 350 Hz/Oil, Mole Ratio 6 7 6 LHSV 2.0 2.0 2.0

Example 1 In this example the catalyst was not presulfided and thedesulfurized feed was Platforms-d under the stated conditions. Thetemperature was increased with time as shown by curve 1 in FIGURE 1 tomaintain the production of platformate having an F-l-O octane number of100. The yield of debutanized reformate declined as shown by curve 1 inFIGURE 2.

Example 2 In this example the catalyst was presulfided by treatment withH S for 2 hours at 900 F. Thiophene was added to the feed to give 100p.p.m. sulfur during the entire run. The results are shown in curve 2 ofFIG- URES 1 and 2.

Example 3 In this example the catalyst was not presulfided but thiopheneequivalent to 300 p.p.m. of sulfur was added to the feed. Afterprocessing 5.4 barrels of feed per pound of catalyst a desulfurized feedwas substituted for 2 barrels per pound. The results are shown in curve3 in FIGURES 1 and 2.

It should be noted that under these relatively severe conditions theoperation according to the invention (i.e., where a sulfurized feed wasused through the run up to 2 barrels per pound of the end) thetemperatures required to obtain a 100 F-l-O product were consistentlylower and increased at the lowest rate. Also, and more importantly, therate of yield decline was much lower.

The catalyst in all runs was regenerable at the end of the runs.However, it should be noted that the catalyst in Example 3 would not beregenerable if the run Were stopped at 5.4 barrels per pound. The reasonfor this will be apparent from FIGURE 3. Here the catalyst was used inthe treatment of a feed containing 300 p.p.m. sulfur and then analyzedfor sulfur. A desulfurized feed was then treated with the same catalystand its sulfur content periodically determined. As shown by the curve inFIGURE 3 the sulfur content of the catalyst comes to a new lowequilibrium value but it requires about 2 barrels of the desulfurizedfeed per pound of catalyst to achieve this end. If the catalyst containsmore than a few hundredths of a percent of sulfur it cannot beregenerated because during the burning, oxides of sulfur are formedwhich permanently impair the activity of the catalyst and which arecorrosive to the metal walls of the reactor and auxiliary equipment.

In operating according to the invention the amount of sulfur in the feedto the Platforming reaction zone should be at least 200 p.p.m. andpreferably 300 p.p.m. based on the feed. This includes any sulfurintroduced with the recycled hydrogen. Higher concentration up to 400p.p.m. or even 500 p.p.m. may be used but are generally not recommendedbecause most plants are not constructed of alloys which are sufiicientlyresistant to corrosion. The specified high sulfur concentration ismaintained throughout the run except for the last approximately 2barrels per pound of catalyst in which a desulfurized feed issubstituted. Thus, for example, if the run length is to be 15 barrelsper pound the sulfur-containing feed is used for about 13 barrels, perpound and the desulfurized feed is used during the period from 13 to 15barrels per pound. The feed used during the last 2 barrels per poundshould be desulfurized to a sulfur level not exceeding about 25 p.p.m.Following the last 2 barrels per pound with desulfurized feed thecatalyst is flushed of hydrocarbons, regenerated by burning off thecarbonaceous deposits, and reused in a new run.

We claim as our invention:

In the semi-regenerative reforming of a heavy naphtha by contact in thevapor phase with a platinum catalyst on a suitable support in thepresence of substantial pressure of hydrogen under dehydrogenatingconditions of temperature to an F-l-O octane number of about 100 for arun length between about 5 and 20 barrels per pound References Cited inthe file of this patent UNITED STATES PATENTS 2,861,944 Coley et al.Nov. 25, 1958 3,006,841 Haensel Oct. 31, 1961 FOREIGN PATENTS 826,909Great Britain Jan. 27, 1960

